In recent years, with advancements in nanotechnology, many innovative biosensors have been developed to effectively and rapidly detect biomolecules. Among them, research and application of magnetic nanoparticles in the field of biomedical science utilizing characteristics of the magnetic nanoparticles and mechanism of their interactions with biomolecules, magnetic sensors for sensing biomolecules, in particular, have also been gradually popularized.
A nanoparticle analysis is a common sensing method used to indirectly measure amount or concentration of a to-be-measured object by attaching magnetic beads with a to-be-measured biomolecule, applying an external magnetic field within a specific range, generating an additional magnetic field using a superparamagnetism of the magnetic beads, and measuring the additional magnetic field generated by the magnetic beads using the magnetic sensor.
In other words, magnetic sensing elements in the magnetic sensor is able to sense a magnetic field variation of the magnetic beads in order to estimate a density of the molecule attached on the magnetic beads. Given that the magnetic beads can only induce magnetic moment in an environment with the external magnetic field in order to generate the additional magnetic field, a magnetic force generator can be used to apply the external magnetic field to the magnetic beads. Because the magnetic sensing elements are also responsive to the external magnetic field generated by the magnetic force generator, finding a way to prevent magnetic sensing elements from influences caused by the external magnetic field generated by the magnetic force generator has become one of major issues to be addressed.